1. Field
The technology relates to addressing the memory on an integrated circuit, such as serial flash memory.
2. Description of Related Art
Serial flash is a flash memory type with a serial interface standard such as Serial Peripheral Interface (SPI). Sequential data communication occurs in compliance with the serial interface. Such a serial device requires fewer external pins than a parallel interface device having a memory of comparable size. For example, to communicate a 24 bit memory address specifying about 16 million memory locations of an 8 bit byte in a 128 megabit memory, a serial flash device compliant with the SPI standard communicates the 24 bit memory address serially through an input pin, rather than in parallel through 24 input pins.
Conventional serial flash uses a 24-bit address stream through the input pin or pins for accessing a memory space up to 128 megabits. Because the number of address bits is a limitation on the addressable memory space, when each addressable location stores an 8 bit byte, the 24-bit address limits the storage capacity to 128 megabits, limiting potential applications.
However, modification of a memory device to expand the range of addressable memory is discouraged, in that any such modification which “breaks” compliance of a memory device with a common standard such as SPI, or with an existing instruction set used with existing products of a company, would result in a burden on existing users already familiar with the common standard or existing instruction set. Accordingly, this adds difficulty to the expansion of the capacity of a memory device.